Photoelectric transfer device

ABSTRACT

A photoelectric transfer device in which an electroconductive layer is formed on a surface of an oxide substrate comprising lead component at a ratio of 30-99.5 mol % as PbO and chromium component at a ratio of 0.5-70 mol %, preferably at a ratio of 60-90 mol % as PbO and a chromium component at a ratio of 10-40 mol %.

BACKGROUND OF THE INVENTION

The present invention relates to a photoelectric transfer device. More particularly, it relates to a photoelectric transfer device in which an electric conductive layer is formed on an oxide comprising lead oxide PbO, chromium oxide Cr₂ O₃ or its derivative.

It has been well known to use varying photoelectric transfer devices utilizing p-n or p-n-p junction of semiconductors or junction of a semiconductor and a metal.

These photoelectric transfer devices need not receive outer electromotive force, because electromotive force is generated from the photoelectric transfer device by exposing it to incident ray.

Such photoelectric transfer characteristic of a dielectric substance has not been disclosed. It has been known that SbS (I) has photoconductivity. Thus, it is necessary to use outer electromotive force for passing photocurrent. It has not been found to use a dielectric substance for studying the photoelectric transfer phenomenon. It has been considered and believed that such photoelectric transfer phenomenon is given by using a dielectric substance.

The inventors have found photoelectric transfer phenomenon of a dielectric substance in studies on oxide dielectric substances.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a photoelectric transfer device in which a dielectric substance is used.

It is another object of the present invention to provide an improved photoelectric transfer device in which a modified dielectric substance is used.

The foregoing and other objects of the present invention have been attained by providing a photoelectric device in which an electroconductive layer is formed on a surface of an oxide substrate comprising lead oxide and chromium oxide and if desired with other additives.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of variations of output voltage to laser power (4880 A incident light);

FIGS. 2 to 8 respectively represent graphs of variations of electromotive force to contents of various additives incorporated in the oxide substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the photoelectric transfer device of the present invention, incident ray input to the oxide substrate is transferred into current and the current is passed through the conductive layer to outside of the device.

When the oxide substrate is a thin film, electromotive force depending upon incident ray is formed to impart photosensitivity. On the other hand, when the oxide substrate is thick, charge storage effect is imparted.

The photoelectromotive force can be increased and the stability of the oxide substrate can be improved by incorporating an additional component in PbO and Cr₂ O₃.

Suitable additional components include perovskite composite oxides such as PbTiO₃, PbZrO₃ as Pb(Zr1/2Ti1/2)O₃ ; monovalent metal compounds such as K₂ CO₃, Li₂ CO₃, Na₂ CO₃, Rb₂ CO₃, Cs₂ CO₃ and Cu₂ CO₃ (CuO); pentavalent metal compounds such as Nb₂ O₅ and Ta₂ O₅ ; tetravalent metal compounds such as TiO₂, SiO₂ and ZrO₂ ; trivalent metal compounds such as Al₂ O₃, and In₂ O₃ ; hexavalent metal compounds such as MoO₃ and WO₃ ; and divalent metal compounds such as BaCO₃, SrCO₃ and ZnCO₃, (ZnO).

The main components PbO and Cr₂ O₃ are blended at a ratio of 30-99.5 mol % of PbO to 0.5-70 mol % of Cr₂ O₃.

The additional component is incorporated at each following ratio to the total of PbO and Cr₂ O₃.

    ______________________________________                                         perovskite composite oxides:                                                                    upto 95 mol %.                                                monovalent metal compounds:                                                                     upto 80 mol % as its carbonate.                               pentavalent metal compounds:                                                                    upto 55 mol % as its oxide of                                                  M .sub.2.sup.1O.sub.5 (M.sup.1 : metal (V))                   tetravalent metal compounds:                                                                    upto 55 mol % as its oxide of                                                  M.sup.2 O.sub.2 (M.sup.2 : metal (IV))                        trivalent metal compounds:                                                                      upto 55 mol % as its oxide of                                                  M .sub.2.sup.3O.sub.3 (M.sup.3 : metal(III))                  hexavalent metal compounds:                                                                     upto 60 mol % as its oxide of                                                  M.sup.4 O.sub.3 (M.sup.4 : metal (VI))                        divalent metal compounds:                                                                       upto 55 mol % as its carbonate.                               ______________________________________                                    

The main components PbO and Cr₂ O₃ and the additional component used in the present invention are preferably fine powders suitable for preparing a sintered dielectric substance having uniform structure.

The mixture is preferably calcined at 400°-500° C. and pulverized into fine powder. The calcined powder is mixed with a binder and molded by a press-molding and the molded product is sintered at 650°-900° C.

The surface of the sintered product is coated with a metal film such as aluminum, silver, copper or alloy, preferably by a vacuum evaporation method. A thickness of the metal film can be selected to be electroconductive and to result in photoelectric transfer such as 0.1 to 100 μm especially about 0.5 μm. The metal film is usually formed by depositing the metal on both surfaces of the dielectric substance.

EXAMPLE 1

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅. These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650° to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm. and a thickness of 1 mm. and a disk having a diameter of 20 mm. and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

The resulting photoelectric transfer device of the present invention was exposed to sunbeams (soft sunbeams) and the resulting photoelectromotive force was measured by a DC voltage meter. The resulting electromotive force was about 50 mV. When the incident ray was shut out to measure the electromotive force, the electromotive force of the device having a thickness of 0.1 mm. was zero whereas one having a thickness of 1 mm. was not zero.

That is, it was found that the photosensitivity was high in the thin film type device whereas the charge storage effect was high in the thick article.

EXAMPLE 2

In accordance with the process of Example 1, a photoelectric transfer device was prepared by the same method at the same ratio of the components except varying a thickness and its photosensitivity was measured. As a result, the photosensitivity was remarkably inferior when thickness was greater than 0.2 mm. whereas the charge storage effect was increased depending upon the increase of the thickness.

EXAMPLE 3

In accordance with the process of Example 1 or 2, a photoelectric transfer device was prepared at the ratio for a composition of Pb₅ CrO₈.

In accordance with the method of Example 1, a photoelectromotive force was measured by using sunbeams (soft sunbeams) as the light source to give 30 mV. The photosensitivity was substantially the same with those of Examples 1 and 2.

EXAMPLE 4

In accordance with the process of Example 1 or 2, a photoelectric transfer device was prepared at the ratio for a composition of PbCrO₄.

In accordance with the method of Example 1, photoelectromotive force was measured by using sunbeams (soft sunbeams) as the light source to give 35 mV. The photosensitivity was substantially the same with those of Example 1 or 2.

In all of the examples, excellent photoelectromotive force was given.

Each photoelectric transfer device was prepared by the process of Example 1 by varying a ratio of PbO to Cr₂ O₃. As results, the photoelectromotive force effect was not substantially found when a ratio of Cr₂ O₃ was higher than 70 mol %.

The photoelectromotive force effect was not substantially found when a ratio of PbO was higher than 99.5 mol %.

The ratios of PbO to Cr₂ O₃ are as follows. A mixed crystal of PbCrO₄ and Cr₂ O₃ is formed when the content of Cr₂ O₃ is excess to the ratio for PbCrO₄. A mixed crystal of Pb₅ CrO₈ and PbO is formed when the content of PbO is excess to the ratio for Pb₅ CrO₈. A mixed crystal of a combination of ones selected from PbO, Cr₂ O₃, Pb₂ CrO₅ and Pb₅ CrO₈ is formed at a ratio of the middle range.

Each laser ray was applied to each of the photoelectric transfer device of Examples 1, 3 and 4 which has a thickness of 0.1 mm. and the relation of the laser power and the output voltage of the photoelectric transfer device was measured. The results are shown in FIG. 1. The intensity of the laser ray was varied in a range of 0 to 70 μW/cm² by using a filter for a wavelength of 4800 A. The output voltage was varied depending upon the variation of the laser power as shown in FIG. 1 wherein the curves (1), (2) and (3) respectively show the results of Examples 1, 2, and 3.

EXAMPLE 5

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅.

As each additional component, PbTiO₃, PbZrO₃ or Pb(Zr1/2Ti1/2)O₃ was respectively incorporated at a range of less than 95 mol %.

These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650° to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm. and a thickness of 1 mm. and a disk having a diameter of 20 mm. and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

Each resulting photoelectric transfer device of the present invention was exposed to laser beam having a laser power of 20 μW/cm² at a wavelength of 4880 A and each photoelectromotive force was measured by a DC voltage meter. The results are shown in Table 1 and plotted in FIG. 2.

As it is clearly understood from Table 2 and FIG. 1, the maximum value was given in a content of the additional component of about 40 mol % and was higher than 1550 μV/cm² in the case of PbTiO₃ ; higher than 2140 μV/cm² in the case of PbZrO₃ and higher than 2100 μV/cm² in the case of Pb(Zr1/2Ti1/2)O₃.

An electromotive force of the device was measured by masking the device from incident ray. When a thickness of the disk was 0.1 mm, the electromotive force was zero. However, when a thickness of the disk was 1 mm, it was not zero. This fact shows that a thin device has high photosensitivity whereas a thick device has high charge storage effect.

                  TABLE 1                                                          ______________________________________                                         Additional                                                                     component Photoelectromotive force (μV/cm.sup.2)                            mol %     PbTiO.sub.3                                                                               PbZrO.sub.3                                                                             Pb(Zr1/2Ti1/2)O.sub.3                            ______________________________________                                          0        150        150      150                                               5        250        320      300                                              10        400        650      600                                              20        850        1220     1200                                             30        1250       1700     1700                                             40        1550       2140     2100                                             50        1400       1910     1900                                             70        1100       940      950                                              90        400        310      300                                              100        0          0        0                                               ______________________________________                                    

EXAMPLE 6

In accordance with the process of Example 5, each photoelectric transfer device was prepared by blending PbO and Cr₂ O₃ to give PbCrO₄ or Pb₅ CrO₈ and adding 10 mol % of Pb(Zr1/2Ti1/2)O₃.

As results, the photoelectromotive forces of the devices were respectively 720 μV/cm² in the case of PbCrO₄ and 660 μV/cm² in the case of Pb₅ CrO₈.

EXAMPLE 7

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅. As an additional component, K₂ CO₃ was incorporated at a range of 5-90 mol %.

These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650° to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm and a thickness of 1 mm. and a disk having a diameter of 20 mm. and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

Each resulting photoelectric transfer device of the present invention was exposed to laser beam having a laser power of 20 μW/cm² at a wavelength of 4880 A and each photoelectromotive force was measured by a DC voltage meter. The results are shown in Table 2 and plotted in FIG. 3.

As it is clearly understood from Table 2 and FIG. 3, the maximum value was given in a content of K₂ CO₃ of about 20 mol % and was higher than 4700 μV/cm². An electromotive force of the device was measured by masking the device from incident ray. When a thickness of the disk was 0.1 mm, the electromotive force was zero. However, when a thickness of the disk was 1 mm, it was not zero. This fact shows that a thin device has high photosensitivity, whereas a thick device has high charge storage effect.

                  TABLE 2                                                          ______________________________________                                         K.sub.2 CO.sub.3                                                                           Photoelectromotive                                                 (mol %)     force (μV/cm.sup.2)                                             ______________________________________                                          0           150                                                                5          2700                                                               10          4000                                                               20          4700                                                               30          4000                                                               40          2000                                                               50          1100                                                               70           200                                                               90            0                                                                100           0                                                                ______________________________________                                    

EXAMPLE 8

In accordance with the process of Example 7, each photoelectric transfer device was prepared by blending PbO and Cr₂ O₃ to give PbCrO₄ or Pb₅ CrO₈ and adding 10 mol % of K₂ CO₃.

As results, the photoelectromotive forces of the devices were respectively, 2820 μV/cm² in the case of PbCrO₄ and 2600 μV/cm² in the case of Pb₅ CrO₈.

EXAMPLE 9

In accordance with the process of Example 7 except using 10 mol % of Li₂ CO₃, Na₂ CO₃, Rb₂ CO₃ or Cs₂ CO₃ instead of K₂ CO₃, each photoelectric transfer device was prepared and each photoelectromotive force was measured.

In the other test, Cu₂ O was used instead of K₂ CO₃. The results are shown in Table 3.

                  TABLE 3                                                          ______________________________________                                         Additional component                                                                           Photoelectromotive                                             (10 mol %)      force (μV/cm.sup.2)                                         ______________________________________                                         K.sub.2 CO.sub.3                                                                               4700                                                           Li.sub.2 CO.sub.3                                                                              3800                                                           Na.sub.2 CO.sub.3                                                                              4200                                                           Rb.sub.2 CO.sub.3                                                                              4000                                                           Cs.sub.2 CO.sub.3                                                                              4050                                                           Cu.sub.2 CO.sub.3 (Cu.sub.2 O)                                                                 3900                                                           ______________________________________                                    

EXAMPLE 10

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅. As an additional component, Nb₂ O₅ was incorporated at a range of 5-80 mol %.

These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650°to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm and a thickness of 1 mm. and a disk having a diameter of 20 mm. and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

Each resulting photoelectric transfer device of the present invention was exposed to laser beam having a laser power of 20 μW/cm² at a wavelength of 4880 A and each photoelectromotive force was measured by a DC voltage meter. The results are shown in Table 4 and plotted in FIG. 4.

As it is clearly understood from Table 4 and FIG. 4, the maximum value was given in a content of Nb₂ O₅ of about 20 mol % and was higher than 1700 μV/cm². An electromotive force of the device was measured by masking the device from incident ray. When a thickness of the disk was 0.1 mm, the electromotive force was zero. However, when a thickness of the disk was 1 mm, it was not zero. This fact shows that a thin device has high photosensitivity, whereas a thick device has high charge storage effect.

                  TABLE 4                                                          ______________________________________                                         Additional component                                                                           Photoelectromotive                                             Nb.sub.2 O.sub.5                                                                               force                                                          (mol %)         (μV/cm.sup.2)                                               ______________________________________                                         0               150                                                            5               900                                                            10              1500                                                           20              1700                                                           30              1350                                                           40              1000                                                           50              500                                                            60              0                                                              80              0                                                              100             0                                                              ______________________________________                                    

EXAMPLE 11

In accordance with the process of Example 10, each photoelectric transfer device was prepared by blending PbO and Cr₂ O₃ to give PbCrO₄ or Pb₅ CrO₈ and adding 10 mol % of Nb₂ O₅.

As results, the photoelectromotive forces of the devices were respectively, 900 μV/cm² in the case of PbCrO₄ and 720 μV/cm² in the case of Pb₅ CrO₈.

EXAMPLE 12

In accordance with the process of Example 10 except using 10 mol % of Ta₂ O₅ instead of Nb₂ O₅, each photoelectric transfer device was prepared and each photoelectromotive force was measured. The results are shown in Table 5.

                  TABLE 5                                                          ______________________________________                                         Additional component                                                                           Photoelectromotive                                             (10 mol %)      force (μV/cm.sup.2)                                         ______________________________________                                         Nb.sub.2 O.sub.5                                                                               1500                                                           Ta.sub.2 O.sub.5                                                                               1400                                                           ______________________________________                                    

EXAMPLE 13

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅. As an additional component, TiO₂ was incorporated at a range of 5-80 mol %.

These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650° to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm and a thickness of 1 mm. and a disk having a diameter of 20 mm. and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

Each resulting photoelectric transfer device of the present invention was exposed to laser beam having a laser power of 20 μW/cm² at a wavelength of 4880 A and each photoelectromotive force was measured by a DC voltage meter. The results are shown in Table 6 and plotted in FIG. 5.

As it is clearly understood from Table 6 and FIG. 5, the maximum value was given in a content of TiO₂ of about 20 mol % and was higher than 1400 μV/cm². An electromotive force of the device was measured by masking the device from incident ray. When a thickness of the disk was 0.1 mm, the electromotive force was zero. However, when a thickness of the disk was 1 mm, it was not zero. This fact shows that a thin device has high photosensitivity, whereas a thick device has high charge storage effect.

                  TABLE 6                                                          ______________________________________                                         Additional component                                                                           Photoelectromotive                                             TiO.sub.2 (mol %)                                                                              force (μV/cm.sup.2)                                         ______________________________________                                         0               150                                                            5               700                                                            10              1200                                                           20              1400                                                           30              1150                                                           40              800                                                            50              250                                                            60              0                                                              80              0                                                              100             0                                                              ______________________________________                                    

EXAMPLE 14

In accordance with the process of Example 13, each photoelectric transfer device was prepared by blending PbO and Cr₂ O₃ to give PbCrO₄ or Pb₅ CrO₈ and adding 10 mol % of TiO₂.

As results, the photoelectromotive forces of the devices were respectively, 720 μV/cm² in the case of PbCrO₄ and 580 μV/cm² in the case of Pb₅ CrO₈.

EXAMPLE 15

In accordance with the process of Example 14 except using 10 mol % of SiO₂ or ZrO₂ instead of TiO₂, each photoelectric transfer device was prepared and each photoelectromotive force was measured. The results are shown in Table 7.

                  TABLE 7                                                          ______________________________________                                         Additional component                                                                           Photoelectromotive                                             (10 mol %)      force (μV/cm.sup.2)                                         ______________________________________                                         TiO.sub.2       1200                                                           SiO.sub.2       1100                                                           ZrO.sub.2       1150                                                           ______________________________________                                    

EXAMPLE 16

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅. As an additional component, Al₂ O₃ was incorporated at a range of 5-80 mol %.

These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650° to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm and a thickness of 1 mm. and a disk having a diameter of 20 mm. and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

Each resulting photoelectric transfer device of the present invention was exposed to laser beam having a laser power of 20 μW/cm² at a wavelength of 4880 A and each photoelectromotive force was measured by a DC voltage meter. The results are shown in Table 8 and plotted in FIG. 6.

As it is clearly understood from Table 8 and FIG. 6, the maximum value was given in a content of Al₂ O₃ of about 20 mol % and was higher than 900 μV/cm². An electromotive force of the device was measured by masking the device from incident ray. When a thickness of the disk was 0.1 mm, the electromotive force was zero. However, when a thickness of the disk was 1 mm, it was not zero. This fact shows that a thin device has high photosensitivity, whereas a thick device has high charge storage effect.

                  TABLE 8                                                          ______________________________________                                         Additional component                                                                           Photoelectromotive                                             Al.sub.2 O.sub.2 (mol %)                                                                       force (μV/cm.sup.2)                                         ______________________________________                                         0               150                                                            5               500                                                            10              800                                                            20              900                                                            30              650                                                            40              450                                                            50              250                                                            60              0                                                              80              0                                                              100             0                                                              ______________________________________                                    

EXAMPLE 17

In accordance with the process of Example 16, each photoelectric transfer device was prepared by blending PbO and Cr₂ O₃ to give PbCrO₄ or Pb₅ CrO₈ and adding 10 mol % of Al₂ O₃.

As results, the photoelectromotive forces of the devices were respectively, 480 μV/cm² in the case of PbCrO₄ and 380 μV/cm² in the case of Pb₅ CrO₈.

EXAMPLE 18

In accordance with the process of Example 16 except using 10 mol % of In₂ O₃ instead of Al₂ O₃, each photoelectric transfer device was prepared and each photoelectromotive force was measured. The results are shown in Table 9.

                  TABLE 9                                                          ______________________________________                                         Additional component                                                                           Photoelectromotive                                             (10 mol %)      force (μV/cm.sup.2)                                         ______________________________________                                         Al.sub.2 O.sub.2                                                                               800                                                            In.sub.2 O.sub.2                                                                               600                                                            ______________________________________                                    

EXAMPLE 19

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅. As an additional component, WO₃ was incorporated at a range of less than 60 mol %.

These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650° to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm and a thickness of 1 mm. and a disk having a diameter of 20 mm. and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

Each resulting photoelectric transfer device of the present invention was exposed to laser beam having a laser power of 20 μW/cm² at a wavelength of 4880 A and each photoelectromotive force was measured by a DC voltage meter. The results are shown in Table 10 and plotted in FIG. 7.

As it is clearly understood from Table 10 and FIG. 7, the maximum value was given in a content of WO₃ of about 20 mol % and was higher than 2250 μV/cm². An electromotive force of the device was measured by masking the device from incident ray. When a thickness of the disk was 0.1 mm, the electromotive force was zero. However, when a thickness of the disk was 1 mm, it was not zero. This fact shows that a thin device has high photosensitivity, whereas a thick device has high charge storage effect.

                  TABLE 10                                                         ______________________________________                                         Additional component                                                                           Photoelectromotive                                             WO.sub.3 (mol %)                                                                               force (μV/cm.sup.2)                                         ______________________________________                                         0               150                                                            5               1400                                                           10              2200                                                           20              2250                                                           30              1600                                                           40              900                                                            50              300                                                            70              0                                                              90              0                                                              100             0                                                              ______________________________________                                    

EXAMPLE 20

In accordance with the process of Example 19, each photoelectric transfer device was prepared by blending PbO and Cr₂ O₃ to give PbCrO₄ or Pb₅ CrO₈ and adding 10 mol % of WO₃.

As results, the photoelectromotive forces of the devices were respectively, 1350 μV/cm² in the case of PbCrO₄ and 1240 μV/cm² in the case of Pb₅ CrO₈.

EXAMPLE 21

In accordance with the process of Example 19 except using 10 mol % of MoO₃ instead of WO₃, each photoelectric transfer device was prepared and each photoelectromotive force was measured. As a result, excellent photoelectromotive force of 2100 μV/cm² was given in the case of MoO₃.

EXAMPLE 22

Lead oxide PbO and chromium oxide Cr₂ O₃ were used as starting materials and were weighed to give a ratio for a composition of Pb₂ CrO₅. As an additional component, BaCO₃ was incorporated at a range of 5-80 mol %.

These starting materials were blended in wet condition for 10 to 15 hours in a polyethylene pot. The mixture was dried and calcined at 400° to 500° C. for 2 hours. After the calcination, the product was pulverized by a ball mill for 10 to 15 hours to obtain a powder having particle diameter of about 1μ. The calcined powder was admixed with a binder and the mixture was press-molded under a pressure of 1 ton/cm². The molded product was sintered at 650° to 900° C. for 2 hours to obtain a sintered product. A photoelectric transfer device is formed by coating an aluminum film on the surface of the sintered product by a vacuum evaporation method. A shape of the device is a disk having a diameter of 20 mm and a thickness of 1 mm. and a disk having a diameter of 20 mm, and a thickness of 0.1 mm. An electrode having a diameter of 15 mm. and a thickness of 0.5 μm. was formed on each of the upper and lower surfaces of the sintered substrate.

Each resulting photoelectric transfer device of the present invention was exposed to laser beam having a laser power of 20 μW/cm² at a wavelength of 4880 A and each photoelectromotive force was measured by a DC voltage meter. The results are shown in Table 11 and plotted in FIG. 8.

As it is clearly understood from Table 11 and FIG. 8, the maximum value was given in a content of BaCO₃ of about 20 mol % and was higher than 1200 μV/cm². An electromotive force of the device was measured by masking the device from incident ray. When a thickness of the disk was 0.1 mm, the electromotive force was zero. However, when a thickness of the disk was 1 mm, it was not zero. This fact shows that a thin device has high photosensivity, whereas a thick device has high charge storage effect.

                  TABLE 11                                                         ______________________________________                                         Additional component                                                                           Photoelectromotive                                             BaCO.sub.2 (mol %)                                                                             force (μV/cm.sup.2)                                         ______________________________________                                         0               150                                                            5               600                                                            10              1050                                                           20              1200                                                           30              900                                                            40              600                                                            50              250                                                            60              0                                                              80              0                                                              100             0                                                              ______________________________________                                    

EXAMPLE 23

In accordance with the process of Example 22, each photoelectric transfer device was prepared by blending PbO and Cr₂ O₃ to give PbCrO₄ or Pb₅ CrO₈ and adding 10 mol % of BaCO₃.

As results, the photoelectromotive forces of the devices were respectively, 630 μV/cm² in the case of PbCrO₄ and 500 μV/cm² in the case of Pb₅ CrO₈.

EXAMPLE 24

In accordance with the process of Example 22 except using 10 mol % of SrCO₃ or ZnCO₃ instead of BaCO₃, each photoelectric transfer device was prepared and each photoelectromotive force was measured.

In the other test, ZnO was used instead of ZnCO₃. The results are shown in Table 12.

                  TABLE 12                                                         ______________________________________                                         Additional component                                                                           Photoelectromotive                                             (10 mol %)      force (μV/cm.sup.2)                                         ______________________________________                                         BaCO.sub.3      1050                                                           SrCO.sub.3      900                                                            ZnCO.sub.3 (ZnO)                                                                               800                                                            ______________________________________                                    

As described above, the present invention provides a photoelectric transfer device in which an electroconductive layer is formed on a surface of the oxide substrate comprising lead oxide and chromium oxide. The present invention to also to provide a process for producing a photoelectric transfer device which comprises mixing lead oxide and chromium oxide and sintering the mixture and coating an electroconductive layer on the sintered substrate.

Excellent photoelectromotive force is generated. When it is a thin film, excellent photosensitivity is given, whereas when it is a thick plate, charge storage effect imparts. The elements can be prepared as sintered porcelains by sintering and accordingly, the elements can be prepared in mass production and stable so as to be economical. The photoelectric transfer device has advantageously high strength and high durability which are not found in conventional photoelectric transfer devices.

It is important to form at least two conductive layers as electrodes on the oxide substrate. The conductive layers are usually formed on both surfaces of the oxide substrate in a form of a sheet or a film.

It is also possible to form the separated conductive layers on one surface of the oxide substrate.

The oxide substrate can be formed in various shape such as a sheet, a rod and a film. It is also possible to form the oxide substrate by a vacuum deposition by an electron beam method wherein electron beams are radiated to said specific oxides in vacuum to deposite the evaporated oxides on a supporter. The thickness of the oxide substrate can be about 10μ. 

We claim:
 1. A photoelectric transfer device in which an electroconductive layer having a thickness enabling photoelectric transfer of 0.1 to 100μ is coated on a surface of a solid oxide substrate comprising a lead component at a ratio of 30-99.5 mol % as PbO and an oxide of chromium component at a ratio of 0.5-70 mol %, said substrate being uniformly and integrally associated in a unitary mass as a sheet, rod, plate or film.
 2. A photoelectric transfer device according to claim 1 wherein the oxide substrate comprises a lead component at a ratio of 60-90 mol % as PbO and a chromium component at a ratio of 10-40 mol %.
 3. A photoelectric transfer device according to claim 1 wherein the oxide substrate is a sintered product in a plate form.
 4. A photoelectric transfer device according to claim 3 wherein the electroconductive layer is formed on both surfaces of the sintered product in a plate form.
 5. A photoelectric transfer device according to claim 3 wherein a thickness of the sintered product is less than 0.2 mm.
 6. A photoelectric transfer device according to claim 3 wherein a thickness of the sintered product is greater than 0.2 mm.
 7. A photoelectric transfer device according to claim 1 wherein the oxide substrate is selected from the group consisting of Pb₅ CrO₈, Pb₂ CrO₅, PbCrO₄ and mixtures thereof.
 8. A photoelectric transfer device according to claim 1 wherein a perovskite composite oxide, lead titanate or lead zirconate, is incorporated at the ratio of up to 95 mol % based on the total of PbO and Cr₂ O₃.
 9. A photoelectric transfer device according to claim 1 wherein a monovalent metal compound K₂ CO₃, Li₂ CO₃, Na₂ CO₃, Rb₂ CO₃, Cs₂ CO₃, and Cu₂ CO₃ (CuO) is incorporated at a ratio of up to 80 mol % as its carbonate based on the total of PbO and Cr₂ O₃.
 10. A photoelectric transfer device according to claim 1 wherein a pentavalent metal compound is incorporated at a ratio of up to 55 mol % as M₂ ¹ O₅, M¹ : metal of group V, selected from the group consisting of Nb and Ta, based on the total of PbO and Cr₂ O₃.
 11. A photoelectric transfer device according to claim 1 wherein a tetravalent metal compound is incorporated at a ratio of up to 55 mol % as M² O₂, M² : metal of group IV, selected from the group consisting of Ti, Si or Zr, based on the total of PbO and Cr₂ O₃.
 12. A photoelectric transfer device according to claim 1 wherein a trivalent metal compound is incorporated at a ratio of up to 55 mol % as M₂ ³ O₃, M³ : metal of group III, selected from the group consisting of Al and In, based on the total of PbO and Cr₂ O₃.
 13. A photoelectric transfer device according to claim 1 wherein a hexavalent metal compound is incorporated at a ratio of up to 60 mol % as M⁴ O₃, M⁴ : metal of group VI, selected from the group consisting of Mo and W, based on the total of PbO and Cr₂ O₃.
 14. A photoelectric transfer device according to claim 1 wherein a divalent metal compound is incorporated at a ratio of up to 55 mol % as its carbonate based on the total of PbO and Cr₂ O₃, wherein the divalent metal is Zn, Sr or Ba.
 15. A photoelectric transfer device according to claim 1 wherein the oxide substrate is a film deposited on a supporter by an electron beam method in vacuum.
 16. The photoelectric transfer device of claim 3 wherein the sintered product is formed by sintering at 650°-900° C. 